1. Field of the invention
The present invention relates to continuously variable ratio transmission systems.
It is known to provide a continuously variable ratio transmission system having coaxial system input and output shaft and a continuously variable ratio transmission unit (known as a variator) connected coaxially to the system input shaft and having a coaxial variator output shaft. A mixing epicyclic gear train receives drives from the system input and from the variator output. By appropriate use of clutches or other braking elements, the system can operate in a high-gearing regime or low-gearing regime. Examples of such transmissions can be found in JP-A-6-174033 and JP-A-62-255655.
2. Background Art
Inevitably, small power losses arise from the intermeshing of gears. In order to maximise efficiency, it is therefore desirable to reduce the number of gear meshes, particularly in the mixing epicyclic gear train where the losses can effectively be magnified during operation in a “power recirculation” mode. It is thus an object of the present invention to provide a “coaxial” continuously variable ratio transmission of the type described with a reduced number of gear meshes.
The prior art “coaxial” arrangements also require relatively high gear speeds which in turn demand more expensive bearings and tend to increase wear. It is an object of the present invention to reduce such gear speeds.